The objective of this research is to gain a better understanding of cardiopulmonary function in man by examining pulmonary vascular characteristics, right ventricular mechanics, and rheology of blood flow in the pulmonary circulation. As we have become increasingly aware of the importance of the lung vasculature in a variety of diseases, we have also realized the need for more precise methods of studying the pulmonary circulation. Previous work has shown the necessity of considering the pulsatile quality of blood pressure and flow in order to include the effects of blood inertia and vascular compliance as well as vascular resistance. Therefore, it is planned to use modern techniques of biomathematics and bioengineering to assess pulmonary hemodynamics in patients with heart disease. We propose to measure pulsatile pressure and flow to determine vascular impedance, power dissipation, energy cost of transport, and effective pulmonary vascular resistance of the pulmonary vasculature in selected patients undergoing thoracotomy. Because pressure and flow are consequences of ventricular contractility as well as the state of the vascular system, these measurements will be related to right ventricular function, thereby giving a more complete picture of the pulmonary circulation. Mathematical models of the right heart and pulmonary vasculature developed in this laboratory will be related to new theories of blood flow leading to an integrated model of the right-sided circulation. After rigorous experimental validation, this model will then be used in the clinical evaluation of patients. The relationship already operative in our laboratory between surgery and biomathematics an bioengineering, associated with a computer facility oriented toward biological research, offers a unique opportunity to accomplish this important work. BIBLIOGRAPHIC REFERENCES: Berry, J., Jr., Downie, D.E., and Wilcox, B.R. Single beat estimation of left ventricular source characteristics during systolic ejection. Proceeding of the Biophysical Society, 1976. Lucas, C.L., Wilcox, B.R., Coulter, N.A., Jr. Contrasting pulmonary blood flow profiles in children with atrial and ventricular septal defects. Cardiovascular Research, 10:1-12, 1976.